Pipes are often not readily accessible, either from the inside owing to their small diameter, or from the outside owing to the depth at which they are laid.
Whenever such pipes are found to leak, the leak can be sealed only by means of some device operating between two manholes providing access to the inside of the pipe.
Existing devices for this purpose have many drawbacks, such as the difficulty in repairing the bottom of the pipe, the difficulty in sealing large cracks effectively and with lasting effect, the great deal of time needed to fill an entire section of pipe with sealing product, the need for the extensive surface equipment, and so on.
A previous device aimed at overcoming these drawbacks is described in French Pat. specification No. FR 85 04206. The device described there comprises a middle section the diameter of which is smaller than that of the pipe, and two end sections, front and rear respectively, which are connected to the middle section. Each end section is larger in diameter than the middle section. The device is provided with remote control and is fitted with sealing elements and a scraping mechanism.
However, the device has other drawbacks, the main one being its inability to move along very badly damaged pipes, for instance where part of the pipe has collapsed and only sections thereof still remain intact. In such a case, the device gets stuck in the pipe and cannot move forward. It may furthermore be difficult to retrieve the device by moving it backwards without damaging, sometimes very seriously, the sealing elements, and these must then be replaced.
Moreover, the device cannot be adapted to cater for pipes of various diameters. This is a serious drawback, inasmuch as pipes frequently vary widely in diameter, for example from 150 mm to more than 300 mm.
In addition, the device results in significant amounts of the sealing product being wasted, owing to the presence of a very large injection chamber between the two end sections. This chamber must be entirely filled with product, with the result that much thereof is wasted in the pipe. Furthermore, the pipe has to be cleaned following removal of the device.
Finally, the device does not allow for the repair of large longitudinal cracks, owing to instability of the sealing product which does not set well enough on the pipe walls following application.
Also, the need for extensive surface equipment still exists.
The main object of the present invention is to provide a device for the in situ repair of pipes which are inaccessible from the inside, which device, on the one hand, must allow for the repair even of collapsed pipes and pipes where wall sections have been stripped and are no longer present, without damaging the sealing elements, and, on the other hand, will cater for pipes of various diameters. In addition, the device must avoid any significant waste of the sealing product, whilst also allowing for the repair of large longitudinal cracks. Also no extensive surface equipment should be required.